| Pulsed, KrF (λ = 248 nm) laser irradiation was used to induce the formation of linear arrays of silicon nanoparticles that can extend over millimeter distances. The linear arrays were spaced λ apart under normal irradiance. On flat surfaces, the irradiation induces the formation and clustering of a thin silicon film. The deposited film clusters into nanoparticles, when it is sequentially irradiated, that grow to 2–80 nm in diameter depending on the laser energy density. Control over the Si nanoparticle diameter per substrate to within ±1 nm could be obtained by optimizing the laser beam energy density, the inert gas pressure, and the number of laser pulses.; The scattering of the incident laser beam and the interaction of this scattered light with the incident light, at the surface of the irradiated substrate, is required to induce the self-organization of Si nanoparticles on the substrate surface. The light scattering event can take place in the beam path in route to the substrate by an obstacle in the beam path or at a pre-existing micro-roughness, present on the surface prior to the laser pulse. Laser-induced periodic surface structures (LIPSS) form simultaneously, in the surface plane, with the nanoparticle-ordering phenomenon. LIPSS were found to lie beneath the nanoparticles only when they were self-organized. The LIPSS formation and nanoparticle alignment seemed to be intimately related.; Silicon nanoparticles were formed during pulsed laser ablation under a background atmosphere of Ar gas. The nanoparticles were re-deposited on the target surface by backscattering via collision with the Ar background gas. The nanoparticles redeposited with a spatial dependence, relative to the laser spot, based on the pressure of the ambient, the energy density of the laser pulse, and micro-roughness present on the target surface. Clustering in an O2-Ar, reactive gas atmosphere, resulted in the formation of unique nanostructures that exhibit intense, room temperature photoluminescence at 2.5 and 3.0 eV. The photoluminescence was attributed to radiative luminescence from defect states, i.e., oxygen vacancies in the SiO nanoaggregate. |
